VALORIZATION OF BREWER’S SPENT GRAIN FOR XYLOOLIGOSACCHARIDES PRODUCTION: OPTIMIZED EXTRACTION, CHARACTERIZATION, AND PREBIOTIC POTENTIAL

Brewer's spent grain serves as a valuable source of xylo-oligosaccharides (XOS), compounds that have applications in the food, chemical, and pharmaceutical industries due to their prebiotic properties and potential as sugar substitutes. This study aimed to extract XOS from malt bagasse through enzymatic hydrolysis and evaluate its prebiotic functionality in vitro. Initial characterization of malt bagasse revealed a composition of 14% cellulose, 29% hemicellulose, 24% insoluble lignin, 3.4% soluble lignin, and 20% protein. A Central Composite Design (CCD) was employed to optimize xylan extraction. In this study, the potassium hydroxide (KOH) concentration varied from 5% to 12%, and the heat treatment duration ranged from 30 to 60 minutes at 121°C. These parameters served as the independent variables, while the yield was measured as the response variable. The extracted xylan underwent hydrolysis with an endoxylanase enzyme cocktail at 50°C for 48 hours, resulting in the production of XOS, which were subsequently quantified via ion-exchange chromatography. Optimization results yielded a determination coefficient (R²) of 87.38%, indicating that KOH concentration was the most influential factor in XOS yield, with the duration of heat treatment contributing to a lesser extent. Under optimal conditions (8.5% KOH for 45 minutes), the XOS concentration achieved 362.4 ± 35.4 mg of XOS/L of 2% xylan. When applied as a carbon source, XOS effectively supported the growth of probiotic strains such as Lactobacillus brevis and Bifidobacterium sp. The fermentation of XOS led to the production of organic acids, particularly butyric and propionic acids, both recognized for their beneficial effects on intestinal health. These findings reinforce Brewer's spent grain as a significant source of XOS, highlighting its potential as a functional ingredient for gut health applications. This study demonstrates the potential of using Brewer's spent grain to develop bioactive ingredients that promote health as prebiotics.